to find 9.875, first you must forget the calibration on the ruler, for the inche part. because they divide it into eight parts.
instead of 8 parts, now you have to imagine divide it ( one inch) into ten part
then you count form one end a tenth up until you reach the eighth/10
then .875 is 3/4 of the one/tenth. between the eighth and the ninth.
inches (9) ....1... 2... 3...4 ...5 ... 6... 7... 8... 9...-10 (inches)
............ .................. ..........,5 mid point of one inch ..
....... ............. ............ ............ ......... ...8..3/4 ..9 .. is where you should be
But because it is too small 3/4 of 0ne tenth of an inch, you would not find much difference length
I mean between 9.8 and 9.9 inches.